U.S. patent application number 11/682532 was filed with the patent office on 2008-09-11 for system and method for optimizing roaming in a wireless data network.
This patent application is currently assigned to DELL PRODUCTS, LP. Invention is credited to Joel Adams, Christian Garvin.
Application Number | 20080219208 11/682532 |
Document ID | / |
Family ID | 39741514 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080219208 |
Kind Code |
A1 |
Adams; Joel ; et
al. |
September 11, 2008 |
System and Method for Optimizing Roaming in a Wireless Data
Network
Abstract
A system and method for a mobile client device to associate with
a preferred access point in a wireless network A determination is
made as to whether the mobile client device is stationary within
the wireless network The preferred access point is determined
between the different access points within the wireless network.
The mobile client device associates with the preferred access point
to gain desired access to the wireless network
Inventors: |
Adams; Joel; (Austin,
TX) ; Garvin; Christian; (Round Rock, TX) |
Correspondence
Address: |
LARSON NEWMAN ABEL POLANSKY & WHITE, LLP
5914 WEST COURTYARD DRIVE, SUITE 200
AUSTIN
TX
78730
US
|
Assignee: |
DELL PRODUCTS, LP
Round Rock
TX
|
Family ID: |
39741514 |
Appl. No.: |
11/682532 |
Filed: |
March 6, 2007 |
Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W 48/20 20130101;
H04W 36/32 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00 |
Claims
1. A method comprising: determining whether a mobile client device
is stationary; determining a preferred access point when the mobile
client device is stationary; and associating the mobile client
device with the preferred access point when the mobile client
device is stationary.
2. The method of claim 1 wherein the determining step comprises
determining whether the mobile client device is connected to an
electrical outlet.
3. The method of claim 1 wherein the determining step comprises
determining whether a peripheral is communicating with the mobile
client device.
4. The method of claim 1 wherein the determining step comprises
processing motion sensor signals.
5. The method of claim 1 wherein the determining step comprises
processing satellite positioning signals.
6. The method of claim 1 wherein the determining step comprises
determining whether the mobile client device is connected to an
external video monitor device.
7. The method of claim 6 where the external video device is a video
projector.
8. The method of claim 1 wherein the determining step comprises
determining whether the mobile client device is connected to a
docking station.
9. A mobile client device comprising: an indicator module adapted
to determine whether the mobile client device is stationary; an
access point detection module adapted to perform a roam scan upon
receiving a signal from the indicator module indicating that the
mobile client device is stationary; and a processor coupled to the
indicator module, the processor adapted to associate the mobile
client device with a first access point.
10. The mobile client device of claim 9 wherein a second access
point is within the range of the access point detection module.
11. The mobile client device of claim 10 wherein a signal strength
of the first access point is within an acceptable range.
12. The mobile client device of claim 11 wherein a signal strength
of the second access point is stronger than the signal strength of
the first access point.
13. The mobile client device of claim 12 wherein the second access
point is a preferred access point.
14. The mobile client device of claim 13 wherein the processor
associates with the second access point.
15. A method of roaming a mobile client device in a wireless
network, the method comprising: accessing a wireless network
through a first access point; determining that the mobile client
device is stationary; performing a roam scan to locate a second
access point within the wireless network; and connecting to the
second access point
16. The method of claim 15 wherein a first set of access points
provides the mobile client device with access to the wireless
network while roaming.
17. The method of claim 16 wherein a second set of access points
provides the mobile client device with access to the wireless
network while the mobile client device is stationary.
18. The method of claim 17 wherein the second set of access points
improves a density capability in a centralized location.
19. The method of claim 18 wherein a signal strength for the first
set of access points is stronger than a signal strength of the
second set of access points while the mobile client device is
roaming.
20. The method of claim 18 wherein the signal strength for the
second set of access points is stronger than the signal strength of
the first set of access points while the mobile client device is
stationary.
Description
FIELD OF THE DISCLOSURE
[0001] This disclosure relates generally to wireless network
systems, and more particularly to wireless roaming optimization
based on the hardware state of a mobile client device.
BACKGROUND
[0002] As the value and use of information continues to increase,
individuals and businesses seek additional ways to process and
store information. One option is an information handling system. An
information handling system generally processes, compiles, stores,
and/or communicates information or data for business, personal, or
other purposes. Because technology and information handling needs
and requirements can vary between different applications,
information handling systems can also vary regarding what
information is handled, how the information is handled, how much
information is processed, stored, or communicated, and how quickly
and efficiently the information can be processed, stored, or
communicated The variations in information handling systems allow
for information handling systems to be general or configured for a
specific user or specific use such as financial transaction
processing, airline reservations, enterprise data storage, or
global communications. In addition, information handling systems
can include a variety of hardware and software components that can
be configured to process, store, and communicate information and
can include one or more computer systems, data storage systems, and
networking systems.
[0003] When moving an active wireless mobile client device from one
location to another, the device occasionally needs to switch to a
different Access Point (AP) to optimize a connection with a
wireless network. This process, known as roam scanning, is normally
triggered only when the signal strength of a first AP is very low
and if other available APs have a much higher signal strength in
comparison to the first AP's signal strength. When the signal
strength is low, the throughput is also reduced because the data
rate is lowered to maintain connection quality with a lowered
signal to noise ratio. If a user moves an active wireless device
from one location to another stationary location, there is the
likelihood that the AP currently associated with the mobile client
device will not be the closest one available. If the current AP
associated with the mobile client device is not the closest one
available, throughput in the new stationary location may not be as
high as if the mobile client device associated with an AP closer to
the stationary location. What is more, when that AP reduces its
data rate to communicate with the more distant client, the packet
air time will be longer than otherwise needed for communication
with that client and will reduce the available time for other
clients on the same AP to access the wireless network. So, many
users on the wireless network may see adverse effects if this
client stays in the new location associated to the more distant
AP.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] It will be appreciated that for simplicity and clarity of
illustration, elements illustrated in the Figures have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements are exaggerated relative to other elements.
Embodiments incorporating teachings of the present disclosure are
shown and described with respect to the drawings presented herein,
in which:
[0005] FIG. 1 is a schematic view of an embodiment of a simple
wireless network;
[0006] FIG. 2 is a block diagram of an exemplary embodiment of a
mobile client device; and
[0007] FIG. 3 is a flow chart of an embodiment of a mobile client
device performing a roam scan in a wireless network.
[0008] The use of the same reference symbols in different drawings
indicates similar or identical items.
DETAILED DESCRIPTION OF DRAWINGS
[0009] The following description in combination with the Figures is
provided to assist in understanding the teachings disclosed herein.
The following discussion will focus on specific implementations and
embodiments of the teachings This focus is provided to assist in
describing the teachings and should not be interpreted as a
limitation on the scope or applicability of the teachings. However,
other teachings can certainly be utilized in this application.
[0010] FIG. 1 shows an exemplary embodiment of a wireless network
100 comprising a first access point 102, a second access point 104,
and a third access point 106. A mobile client device 108 moves
throughout the wireless network 100 and gains access to the
wireless network by either the first access point 102, the second
access point 104 or the third access point 106.
[0011] Based on the signal strength of each access point, the
mobile client device 108 preferably associates with the access
point that has the highest signal strength. When the mobile client
device 108 associates with an access point the mobile client device
uses that access point to access the wireless network 100. When the
mobile client device 108 initially attempts to access the wireless
network 100 at position A, the mobile client device performs a roam
scan. For example, the mobile device client 1 08 might measure
during the roam scan that the signal strength of the first access
point is -80 dBm, the signal strength of the second access point
104 is -50 dBm, and the signal strength of the third access point
is -75 dBm. The mobile client device 108 associates with the second
access point 104 in position A, because the signal strength of the
second access point is the strongest at that particular
location.
[0012] As the mobile client device 108 is roaming (moving around in
the wireless network 100) from position A to position B it
continues to associate with the second access point 104 until a
signal strength of the second access point is significantly low (no
longer in an acceptable range), such as -70 dBm, or the signal
strength of either the first access point 102 or the third access
point 106 is higher by a certain amount, such as 20 dB more, in
comparison to the signal strength of the second access point, The
mobile client device 108 performs multiple roam scans as it travels
(roams) around the wireless network 100 if the signal strength is
below the acceptable threshold. For example, when the mobile client
device 108 becomes stationary at position B, the mobile client
device determines that the signal strength of the second access
point 104 is below an acceptable threshold, such as -70 dBm, and
therefore performs a roam scan and determines that the signal
strength for the first access point 102 is -60 dBm, the signal
strength for the second access point 104 is -80 dBm, and the signal
strength for the third access point 106 is -75 dBm. When the mobile
client device 108 performs the roam scan while at position B, the
mobile client device will then associate with the first access
point 102 because the first access point has the best signal
strength at position B, and is also 20 db better than the signal
strength of the second access point 104.
[0013] For example, at position C the signal strength of the first
access point 102 is -65 dBm, the signal strength of the second
access point 104 is -70 dBm, and the signal strength of the third
access point 106 is -50 dBm. Under the typical standards for
associating with access points (the standard used while roaming
around in the wireless network 100) the mobile client device 108
would not change associations from the first access point 102 to
the third access point 106 when stationary at position C, The
mobile client device 108 would not re-associate because the signal
strength of the first access point 102 is not below -70 dBm and the
signal strengths of the second access point 104 and the third
access point 106 are not more than 20 dB greater than the signal
strength of the first access point. With the mobile client device
108 not associating with the third access point 106, which has the
best signal strength, the throughput of the mobile client device is
decreased because the signal received by the mobile client device
is not as great as possible Also, if there are other clients in the
wireless network 100 and they are associated with the first access
point 102, their throughput will also be decreased because the
mobile client device 108 will take up more throughput capacity than
is necessary.
[0014] Thus, when the mobile client device 108 is triggered by
knowledge that it is stationary at position C, it performs a roam
scan to determine the preferred access point During the roam scan
the mobile client device 108 determines which access point has the
best signal strength and associates with that access point Using
the signal strengths for position C stated above the mobile client
device 108 associates with the third access point 106, because the
signal strength of the third access point is stronger than the
signal strength of both the first access point 102 and the second
access point 104.
[0015] In another embodiment the larger circles 110, 112, and 114
of the first access point 102, the second access point 104, and the
third access point 106 represent 8021 1 g or 802.11n access point
ranges and the smaller circles 116, 118, and 120 represent 802.11a
access point ranges (higher frequency band so less signal
propagation). In this embodiment when the mobile client device 108
detects it is stationary at position C it performs a roam scan and
selects the best frequency band of the access points in the
wireless network 100. While stationary at position C the mobile
client device 108 selects the 802.11a band to connect with the
wireless network 100, so that the mobile client device has the best
data throughput possible at the current location in the wireless
network.
[0016] In another embodiment the wireless network 100 has multiple
sets of access points to allow the best connection possible for the
mobile client device 108. In this embodiment there is a first set
of access points in hallway areas of a building, such as along the
line from position A to position B, and a second set of access
points deployed for the purpose of improving a density capability
within a classroom or cubicle environment of the building, such as
position C. The first set of access points is the combination of
the first access point 102 and the second access point 104, and the
second set of access points is the third access point 106. The
density capability is the ability of an access point within the
wireless network 100 to provide a high quality signal to a large
number of clients within a small area. In these cases the mobile
client device 108, upon determination that mobility has ceased,
attempts to switch to the preferred access point for non-mobile use
by performing a roam scan.
[0017] FIG, 2 shows a block diagram of an exemplary embodiment of a
mobile client device 200 comprising an indicator module 202, an
access point detection module 204, and a controller 206, such as a
wireless controller. In different embodiments the mobile client
device 200 is attached to any combination of the following devices
an electrical outlet 208, a peripheral 210, an external video
monitor device 212, a motion detector device 214, a Global
Positioning System (GPS) 216, and a docking station 218. The
peripheral 210 can be a Bluetooth mouse, a Universal Serial Bus
(USB) mouse or any other type of peripheral that can be attached to
the mobile client device 200. The external video monitor 212 can be
any video device such as a video projector. The indicator module
202 determines whether the mobile client device 200 is stationary
within the wireless network 100 of FIG. 1 using triggers from any
of the devices stated above. After determining that the mobile
client device 200 is stationary, the indicator module 202 sends a
signal to the access point detection module 204 indicating that the
mobile client device is stationary Then the access point detection
module 204 performs a roam scan to locate all of the available
access points in the range of the mobile client device 200. The
access point detection module 204 selects the preferred access
point from the available access points in the wireless network 100
of FIG. 1 and relays the information about the preferred access
point to the controller 206. The controller 206 then associates
with the preferred access point selected by the access point
detection module 204, and the mobile client device 200 uses the
preferred access point to connect with the wireless network 100 of
FIG. 1.
[0018] The mobile client device 200 may assume that it is
stationary upon the occurrence of one or more conditions. For
example, the mobile client device 200 may assume that it is
stationary when it is plugged in to the electrical outlet 208 for
charging or when it is attached to the docking station 218 when it
is returned to the `home base`. Therefore, when a charger from the
electrical outlet 208 or when the docking station 218 is attached
to the mobile client device 200, logic located in a wireless card
or elsewhere can detect this event and initiate a roam scan to
associate with the best possible access point. A secondary trigger
event is when the peripheral 210, such as a Bluetooth (BT) mouse, a
Universal Serial Bus (USB) mouse, or any other pointing device is
attached to the mobile client device 200, which indicates that the
system has come to rest on a surface Also another trigger event is
when the external video monitor device 212, such as a video
projector, is attached to the mobile client device 200 An
additional indication that the mobile client device 200 is
stationary is given by the motion detector device 214 that is
attached to the mobile client device. The transition from moving
(roaming) for many seconds and then not moving for a few seconds is
another use based on the motion sensor signals. Another trigger is
to assume if a client is associated to the same access point for
many minutes (5-10) after previously roaming from a different
access point, then it is no longer moving significantly and should
do a roam scan to assure best access point in use. Further, using
satellite positioning signals, such as from the Global Positioning
System (GPS) 216 using assisted modes with a Wireless Wide Area
Network (WWAN), could also be used to determine that the client is
no longer moving.
[0019] FIGS. 3 shows a flow chart 300 of an exemplary method to
associate the mobile client device 108 with the preferred access
point within the wireless network 100. The diagram and example
shows a selection based on highest signal strength, but other
methods could be used to determine the best candidate access point
(Some examples are highest signal strength, highest signal to noise
ratio, preferred frequency band, preferred access point type, and
highest estimated data rate). In step 302, the mobile client device
108 determines whether it is stationary, which is done by any of
the ways stated above. In step 304, the mobile client device
performs a roam scan, to scan for and find all of the available
access points The mobile client device 108 determines which access
point is the best candidate access point in step 306. In step 308,
the mobile client device 108 determines whether the best candidate
access point is the current access point that the mobile client
device is associated with. If the best candidate access point is
not the current access point, then the mobile client device
associates with the best candidate access point in step 310.
However, if the best candidate access point is the current access
point, then the mobile client device 108 continues to associate
with the current access point in step 312.
[0020] Although only a few exemplary embodiments have been
described in detail above, those skilled in the art will readily
appreciate that many modifications are possible in the exemplary
embodiments without materially departing from the novel teachings
and advantages of the embodiments of the present disclosure.
Accordingly, all such modifications are intended to be included
within the scope of the embodiments of the present disclosure as
defined in the following claims in the claims, means-plus-function
clauses are intended to cover the structures described herein as
performing the recited function and not only structural
equivalents, but also equivalent structures
* * * * *